Enclosures which are to be maintained at relatively low predetermined temperature conditions normally utilize conventional refrigeration systems employing compressors, and condenser and evaporator coils, wherein heat is removed from the enclosures to be cooled by the evaporator through the operation of the conventional refrigeration cycle. Coolers, such as used in restaurants, grocery stores, and the like which are of relatively large size and of the "walk-in" type require refrigeration apparatus of relatively high capacity utilizing large compressor motors of several horse power. With increasing electrical power rates, the cost of operating such refrigeration circuits is becoming increasingly expensive and the owners of such coolers are anxious to reduce operating costs, if possible.
In northern climates outdoor atmospheric temperatures are often below 40.degree. F. during significant portions of the year, and as the temperature within many coolers is approximately 40.degree. F. during normal conditions ambient atmospheric air could be used for cooling purposes, rather than the usual refrigeration circuit, if apparatus is available for efficiently introducing the ambient atmospheric air into the enclosure to be cooled without creating undesirable effects within the cooler and wherein the temperature within the cooled enclosure can be accurately maintained within close tolerances. Cool atmospheric air has been utilized for refrigeration purposes for many years, and it is also known to use electric fans for drawing atmospheric air into a cooler, examples of such installations being shown in U.S. Pat. Nos. 1,693,200 and 1,600,522, respectively. Also, U.S. Pat. No. 2,216,873 discloses a cooled enclosure utilizing ambient air for cooling, thermostatic valves being employed to control the air movement.
More sophisticated apparatus for introducing ambient atmospheric air into an enclosure to be cooled is shown in U.S. Pat. Nos. 4,023,947 and 4,250,716, and these patents disclose electrical circuits controlling fans for the introduction of ambient atmospheric air into the enclosure which are also correlated to the conventional refrigeration control circuit such that the auxiliary ambient air cooling system is only utilized when the atmospheric air is below a predetermined temperature, such as 40.degree. F., and at higher ambient temperatures cooling will be produced by the refrigeration circuit in the conventional manner. With auxiliary ambient air cooling systems such as shown in the aforementioned patents, it has been found that the placing of the ambient air supply fan within the enclosure to "draw" the ambient air into the enclosure severely limits the efficiency and capacity of the apparatus in that the length of the fan inlet duct must be relatively great, and high air frictional resistance is encountered, substantially reducing the effective capacity of the auxiliary cooling system.
A further deficiency of the prior art devices results from the fact that auxiliary cooling systems introducing ambient air into the cooled enclosure do not provide for the exhausting of an equal amount of air therefrom in order to prevent a superatmospheric pressure within the enclosure being cooled. Thus, a superatmospheric pressure is produced within the enclosure causing an excessive loss of cool air when the enclosure doors are opened, and also producing undesirable door action and movement, tending to open, and maintain the door open, and complicate door latching and closing.
It is an object of the invention to provide apparatus for utilizing cool ambient atmospheric air for cooling an enclosure wherein the apparatus is readily installable in existing structure, and wherein a wide variety of installations may be accomodated without adversely affecting the efficiency of the apparatus.
A further object of the invention is to provide apparatus for utilizing ambient atmospheric air for cooling wherein the atmospheric air is forced into the enclosure to be cooled, rather than drawn therein, assuring a high efficiency of air handling and transfer regardless of the wall thickness of the enclosure or other unusual installation characteristics.
An additional object of the invention is to provide apparatus for utilizing ambient atmospheric air for cooling wherein atmospheric air is introduced into the cooled enclosure at a rate substantially equal the rate air is exhausted therefrom wherein the pressure within the cooled enclosure remains substantially normal during operation of the apparatus.
Yet another object of the invention is to provide apparatus for utilizing ambient exterior atmospheric air for cooling purposes wherein a preassembled panel is located within the cooled enclosure communicating with air ducts formed in the enclosure wall whereby a professional and attractive appearance is maintained, and wherein installation can be achieved without requiring unusual skills.
In the practice of the invention a pair of spaced, substantially parallel, openings are formed in the wall of the enclosure to be cooled wherein the openings communicate with the ambient atmospheric air. Insulated ducts are located within the openings, and the duct's inner ends communicate with air inlet and outlet openings defined in a panel attached to the inner wall of the enclosure. The panel includes an aligned inlet opening having a grill disposed thereover whereby cool ambient air may pass therethrough into the enclosure, and the panel outlet, or exhaust opening, is aligned with an exhaust fan mounted upon the panel for displacing air from the enclosure through self-closing louvres formed in the panel outlet opening into the aligned air duct. Temperature sensing control means are mounted upon the panel intermediate the air inlet and outlet opening, and the control means include temperature sensing bulbs within the enclosure and also sensing the exterior ambient atmospheric air wherein, upon predetermined temperature conditions existing within the enclosure, and within the atmospheric air, simultaneous operation of an air supply fan and the exhaust fan occurs.
A housing is located at the outer end of the air duct communicating with the panel inlet opening, and an air supply fan is located therein in communication with the associated air duct. A filter within the housing filters air drawn therein by the air supply fan wherein the filtered air is forced into the air duct and through the panel grill into the enclosure being cooled.
A weather shield is mounted upon the outer end of the other air duct communicating with the exhaust fan, and the weather shield includes a screen preventing insects, birds, and foreign matter from entering the associated air duct, and the shield includes a downwardly disposed opening through which exhausted air passes.
As the air flow capacities of the air supply fan and the exhaust fan are substantially equal, and as these fans operate simultaneously, the introduction of cooled ambient atmospheric air into the enclosure while simultaneously exhausting air therefrom at an equal rate prevents a superatmospheric pressure from occurring within the enclosure resulting in a high air flow efficiency through both fans, and preventing problems which arise when a superatmospheric pressure, even though small, exists within the cooled enclosure.